110 lines
3.1 KiB
C++
110 lines
3.1 KiB
C++
#include "references.hh"
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#include <cstdlib>
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#include <map>
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#include "archive.hh"
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#include "hash.hh"
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#include "util.hh"
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namespace nix {
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static unsigned int refLength = 32; /* characters */
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static void search(const unsigned char* s, size_t len, StringSet& hashes,
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StringSet& seen) {
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static bool initialised = false;
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static bool isBase32[256];
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if (!initialised) {
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for (unsigned int i = 0; i < 256; ++i) isBase32[i] = false;
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for (unsigned int i = 0; i < base32Chars.size(); ++i)
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isBase32[(unsigned char)base32Chars[i]] = true;
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initialised = true;
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}
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for (size_t i = 0; i + refLength <= len;) {
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int j;
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bool match = true;
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for (j = refLength - 1; j >= 0; --j)
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if (!isBase32[(unsigned char)s[i + j]]) {
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i += j + 1;
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match = false;
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break;
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}
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if (!match) continue;
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string ref((const char*)s + i, refLength);
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if (hashes.find(ref) != hashes.end()) {
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debug(format("found reference to '%1%' at offset '%2%'") % ref % i);
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seen.insert(ref);
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hashes.erase(ref);
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}
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++i;
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}
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}
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struct RefScanSink : Sink {
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HashSink hashSink;
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StringSet hashes;
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StringSet seen;
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string tail;
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RefScanSink() : hashSink(htSHA256) {}
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void operator()(const unsigned char* data, size_t len);
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};
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void RefScanSink::operator()(const unsigned char* data, size_t len) {
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hashSink(data, len);
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/* It's possible that a reference spans the previous and current
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fragment, so search in the concatenation of the tail of the
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previous fragment and the start of the current fragment. */
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string s =
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tail + string((const char*)data, len > refLength ? refLength : len);
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search((const unsigned char*)s.data(), s.size(), hashes, seen);
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search(data, len, hashes, seen);
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size_t tailLen = len <= refLength ? len : refLength;
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tail = string(tail, tail.size() < refLength - tailLen
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? 0
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: tail.size() - (refLength - tailLen)) +
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string((const char*)data + len - tailLen, tailLen);
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}
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PathSet scanForReferences(const string& path, const PathSet& refs,
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HashResult& hash) {
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RefScanSink sink;
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std::map<string, Path> backMap;
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/* For efficiency (and a higher hit rate), just search for the
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hash part of the file name. (This assumes that all references
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have the form `HASH-bla'). */
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for (auto& i : refs) {
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string baseName = baseNameOf(i);
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string::size_type pos = baseName.find('-');
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if (pos == string::npos) throw Error(format("bad reference '%1%'") % i);
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string s = string(baseName, 0, pos);
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assert(s.size() == refLength);
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assert(backMap.find(s) == backMap.end());
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// parseHash(htSHA256, s);
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sink.hashes.insert(s);
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backMap[s] = i;
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}
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/* Look for the hashes in the NAR dump of the path. */
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dumpPath(path, sink);
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/* Map the hashes found back to their store paths. */
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PathSet found;
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for (auto& i : sink.seen) {
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std::map<string, Path>::iterator j;
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if ((j = backMap.find(i)) == backMap.end()) abort();
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found.insert(j->second);
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}
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hash = sink.hashSink.finish();
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return found;
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}
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} // namespace nix
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